1. Field of the Invention
The present invention relates to a three-dimensional input device for scanning an object by projecting a detection light on the object and outputting data specifying the object shape.
2. Description of the Related Art
Three-dimensional input devices of the non-contact type known as rangefinders are used for data input to computer graphics systems and computer-aided design systems, physical measurement, and visual recognition for robots and the like, due to their high speed measurement capability compared to contact type devices.
The slit projection method (also referred to as light-section method) is known as a suitable measurement method for rangefinders. This method produces a distance image (three-dimensional image) by optically scanning an object, and is one type of active measurement method which senses an object by illuminating the object with a specific detection light. A distance image is a collection of pixels expressing the three-dimensional position at a plurality of parts on an object. In the slit projection method, the slit light used as the detection light is a projection beam having a linear band-like cross section. A part of an object is illuminated at a specific moment during the scan, and the position of this illuminated part can be calculated by the trigonometric survey method from the light projection direction and the high luminance position on the photoreceptive surface (i.e., photoreception direction). Accordingly, a group of data specifying the object shape can be obtained by sampling the luminance of each pixel of the photoreceptive surface.
In rangefinders the distance to an object is measured and the detection light projection angle range is adjusted. In other words, an operation control is executed to set the projection light start and end angle position so that the entirety of an object reflected on the photoreceptive surface becomes the scanning range in accordance with the image sensing magnification and the object distance. In sampling the luminance of the photoreceptive surface, methods are known which limit the object of a single sampling not to the entire photoreceptive surface but to a part of the area where detection light is expected to enter, and shifts this area for each sampling. Such methods are capable of scanning at high speed by reducing the time required per sample, and further reduce the load on the signal processing system by decreasing the amount of data.
However, in conventional rangefinders, when a measurement object extends beyond a measurable range in the depth direction, an operator must change the field angle by adjusting the focus or zooming, then re-measuring. As the field angle broadens, the measurable range in the depth direction also broadens, but resolution declines. When part of the photoreceptive surface is the target of a single sampling, the measurable range broadens if this target area broadens. As a result, scanning speed is reduced and the data processing load increases.
Accordingly, a first objective of the present invention is to allow three-dimensional data input for an entire object with the same resolution as when the depth dimension is small even when the depth dimension of the object is large.
In addition to the foregoing, in rangefinders the detection light projection intensity is adjusted for the main measurement by performing a preliminary measurement. In other words, an operation setting is executed wherein the detection light is projected to a part of the image sensing range and the projection intensity is optimized in accordance with the amount of the detection light entering the photoreceptive surface.
In conventional devices, however, when an object used as a measurement object has non-uniform reflectivity, i.e., when there is a large divergence between the high and low reflectivity levels of the object, the detection light reception information corresponding to that part of the object attains saturation or attains a solid level (non-responsive), such that the shape of that area cannot be measured. In this instance, measurement must be performed began to obtain the shape data of the entire object.
Accordingly, a second objective of the present invention is to provide a three-dimensional input device capable of obtaining three-dimensional data with a precision identical to that of an object with uniform reflectivity without receiving operation specifications a plurality of times even when there are marked differences in reflectivity depending on the part of the object.
In accordance with the first objective noted above, in one exemplary embodiment of the present invention, the detection light projection angle range is automatically changed, and a plurality of scans are performed. As a result, suitable photoreception information can be obtained by other scans even at the parts of the object from which effective photoreception information cannot be obtained by a particular scan. In other words, the number of scans is theoretically expanded many fold by combining the measurable photoreception range in the depth direction with the measurable photoreception range in each scan.
In accordance with the foregoing embodiment of the present invention, a three-dimensional input device comprises a light projecting means for projecting detection light, and an image sensing means for receiving the detection light reflected by an object and converting said received light to electrical signals, which scans an object periodically while changing the projection direction of the detection light, and consecutively performs a plurality of scans at mutually different detection light projection angle ranges in accordance with the specifications at the start of operation. The specifications at the start of the operation are set by control signals produced by operating a switch or button, or received from an external device.
In accordance with the second objective noted above, in a second exemplary embodiment of the present invention, the projection intensity is automatically changed, and a plurality of scans are performed. As a result, suitable photoreception information can be obtained at other projection intensities even for an area on an object for which suitable photoreception information cannot be obtained at a particular projection intensity. In other words, the amount of entrance light dependent on the reflectivity of a target area can be made to conform to the dynamic range of image sensing and signal processing in at least a single scan. As such, it is possible to measure the shape of the entire area of the measurement range of an object by selecting suitable photoreception data for each part of an object from among photoreception information of a plurality of scans. The objects of the present invention are attained at the moment photoreception information is obtained for a plurality of scans, and the selection of suitable photoreception information can be accomplished within the three-dimensional input device, or by an external device.
Moreover, in the second exemplary embodiment of the present invention, the photo electric conversion signals obtained by a first scan are amplified by different amplification factors. As a result, photoreception information is obtained which is equivalent to the information obtained by a plurality of scans at different projection intensities, and allows the selection of suitable photoreception information for each part of an object.
In accordance with the second exemplary embodiment of the present invention, a three-dimensional input device comprises a light projecting means for projecting detection light, and an image sensing means for receiving the detection light reflected by an object and converting the received light to electrical signals, which scans an object periodically while changing the projection direction of the detection light, and consecutively projects the projection light at different intensities for each of a plurality of scans in accordance with specifications at the start of operation. The specifications at the start of the operation are set by control signals produced by operating a switch or button, or received from an external device.
Additional objects and advantages and novel features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following.